1. Field of the Invention
The present invention relates to motor-driven planers and, more particularly, motor-driven planers adapted to be mounted to multipurpose woodworking tools.
2. Prior Art
Motor-driven planers typically are used for planing wood stock which is relatively wide, on the order of 3 to 12 inches. Such planers include a housing having an interior chamber and a blade member rotatably mounted to the housing and extending transversely of the interior chamber. The blade member is generally cylindrical in shape and includes a plurality of elongated cutting blades which are removably mounted to an axle. The blade member includes an end protruding through the housing adapted to be coupled to an electric motor which is either mounted to the housing and drives the blade member directly, or is mounted remotely from the housing and drives the blade member through a coupling member.
Motorized planers also typically include a table which supports the wood stock as it is fed into the interior chamber to engage the rotating blade member. The table is substantially flat and is positioned within the interior chamber beneath the blade member. The table is joined to the housing by elevating means which typically includes a plurality of jack screws rotatably mounted to the housing and joined to the table by connector nuts. Rotation of the jack screws displaces the nuts, causing the table to be elevated or lowered relative to the blade member. The table is vertically adjusted to vary the cutting or planing depth of the blade member, and to accommodate stock of varying thicknesses.
A disadvantage of motorized planers which utilize jack screws for elevating the tables is that the jack screws must be oriented vertically within the interior chamber and parallel to each other with high precision. Should the jack screws be slightly skewed relative to each other, the table will bind as it is displaced upwardly or downwardly. Since the relative distance between one jack screw and another would vary along its length in such a situation, a lateral force would be exerted between the connector nuts, mounted to the table and thereby fixed relative to each other, and the jack screws as the table is vertically displaced. The requirement for high precision in the alignment of jack screws relative to one another greatly increases the cost of fabrication of motorized planers and often results in a total cost which renders such planers undesirable for use by the non-commercial woodworker or hobbyist.
Another disadvantage with such table elevating mechanisms is that is is difficult to vary the distance between the surface of the table and the cutting blades of the blade member with high precision. Typically, a depth gauge is provided which consists of a vertical scale attached to a side of the housing adjacent the table and an indicator arrow attached to the table. Displacement of the table causes the arrow to move relative to the scale. While such a scale is acceptable for large displacements on the order of 1/2 inch and greater, such a scale is not acceptable for displacements less than approximately 3/8 inches.
An additional disadvantage of such table elevating mechanisms for motorized planers is that occasionally the table becomes inclined or skewed relative to the position of the blade member, which can result in wood stock being planed such that the resultant thickness of the planed stock varies across its width. Adjustment of jack screws often requires the disengagement of one or more jack screws from a drive mechanism and the rotation of the individual jack screw to level the table properly. In many table elevating mechanisms for planers or other types of woodworking tools, the jack screws each include sprockets which are joined by a common sprocket chain such that rotation of one jack screw by an external source of power results in synchronous rotation of the other jack screws. With such devices, adjustment of a single jack screw requires the removal of the drive chain from the sprockets which may necessitate the separation of the sprocket chain by removing a master link, a difficult and time-consuming operation.
Motorized planers also typically include feed mechanisms which comprise rollers positioned upstream and downstream of the blade member, rotatably attached to the housing and extending transversely of the interior chamber. The rollers engage and propel stock along the table beneath the blade member. The rollers typically are driven by external means such as a hand crank or an electric motor. A disadvantage of many types of feed mechanisms is that the rollers require complex apparatus for raising or lowering their position relative to the blade member, or for exerting a downward force on the stock. Such apparatus is often complicated in structure and greatly increases the overall expense of the planer.
While virtually all types of motorized woodworking devices create a problem of sawdust or wood chip removal, the problem is particularly severe for motorized planers, especially if a relatively deep planing operation is performed on a relatively wide piece of stock. Since the blade member is rotated in a direction which is counter to the direction of feed of the stock, the wood chips tend to be driven back toward the user, covering the clothes of the user and presenting a possible hazard of contacting the user's face and eyes. To remedy the situation, motorized planers include a chip shield which consists of an elongated piece of metal or plastic having an arcuate contour and mounted to the housing to extend transversely of the interior chamber adjacent and upstream of the blade member such that the shield curves about an upstream portion of the periphery of the blade member.
The chip shield forms a passageway with the adjacent portion of the outer periphery of the blade member such that, when the planing operation is performed, chips are pumped by the rotating action of the blades along the passageway and are propelled forwardly within the interior chamber downstream of the blade member. While a chip shield changes the direction of chip travel during the planing operation so that the chips are not propelled rearwardly toward the operator, the chips are still propelled out of the planer and clutter the work area surrounding the motorized planer.
Many motorized planers are designed to utilize the head stock or main electric motor of larger, multipurpose woodworking systems. Typically, the planer includes means for mounting the planer housing to the larger woodworking system adjacent the head stock, and the blade member includes an end adapted to be joined to the output shaft of the head stock by a coupling member.
While such planers are desirable in that they may utilize the head stock of existing woodworking machinery, there are some disadvantages. For example, such motorized planers often require an auxiliary source to power the feed mechanism and therefore require the operator to actuate two switches to start or stop the device; a main power switch for actuating the head stock motor which drives the blade member, and a secondary switch which actuates the feed mechanism. A second disadvantage is that planers utilizing the head stocks of larger woodworking tools often require coupling members which provide an offset drive so that the output shaft of the head stock can be coupled to the blade member. Such offset drive coupling members are often expensive and result in power transmission losses.
Accordingly, there is a need for a motorized planer which can be mounted directly to a larger, multipurpose woodworking tool, which is simple in construction, which utilizes the head stock of the multipurpose tool, and utilizes a simple and relatively inexpensive coupling member, and which includes a single master switch for actuating both the head stock motor and an auxiliary drive motor. Furthermore, there is a need for a motorized planer having a table elevated by jack screws which does not require precision mounting of the jack screws to the planer housing to prevent binding and which provides a relatively high precision depth gauge adjustment. Furthermore, there is a need for a motorized planer having a chip removal system which eliminates the clutter and contamination of the work area by wood chips generated during the planing operation.